The Cow Pledge (or "Moo Mooooo") is the pledge taken by every member when or if they wish to join the CMC. In English it is:

I solemly swear to be super duper cowy wowy moo cult person great!

However the original is in CowSpeak and is used in all official business, including new swearing in of new members. The pledge dates back to the 14th century (a couple of days ago) and has evolved into a deeply important item in the CMC's cultural development.